Impossible differentials in Twofish

Niels Ferguson

Twofish Technical Report #5, October 1999.

Abstract

We show how an impossible-differential attack, first applied to DEAL by Knudsen, can be applied to Twofish. This attack breaks six rounds of the 256-bit key version using 2²⁵⁶ steps; it cannot be extended to seven or more Twofish rounds.

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